The development of minimally invasive methods and devices over recent years has revolutionized the practice of medicine. These methods and devices allow medical professionals to perform a wide variety of procedures while minimizing trauma to the patient. Access needles are used in connection with certain minimally invasive medical procedures. These needles may include a tubular cannula body that can form a conduit between a target site within the body of a patient and a location outside of the patient's body. This conduit can subsequently be used by a medical professional for performing certain procedures in connection with the target site or for running a wire guide therethrough.
An access needle may include a stylet in the lumen of its cannula to avoid inadvertent sample collection at the distal end of the cannula, to provide a sharp tip capable of making a puncture, and to provide some reinforcement to the cannula as it travels to the target site within the body. After the distal end of the needle arrives at its target location within the body, the stylet may be withdrawn, thereby clearing a space through the cannula lumen where, for example, a wire guide may be placed. A medical professional performing such a procedure must be able to determine the exact location of the distal end of the cannula to be sure that it has arrived at the precise target site within the body of the patient.
One method useful for determining the location of the distal end of the cannula within the patient's body is carried out using endoscopic ultrasound (EUS). EUS provides a medical professional with the ability to visualize the location of the distal end of the needle within the patient's body without requiring an open incision, use of large-bore needles, or percutaneous trocars. If this method is used for location purposes, the access needle may comprise an echogenic tip at its distal end. Ideally, EUS can then be used to determine the location of the echogenic tip. However, EUS technology is not always capable of providing the medical professional with precise location data. Thus, it could be advantageous to couple EUS with a different form of location technology either to supplement the EUS data or provide location data in the event that EUS is unsuccessful.
In this regard, fluoroscopy may be used as an additional method to determine the location of the distal end of a needle within a patient's body. In one aspect, fluoroscopy may be used to detect a dye or contrast fluid that has been placed within the patient's body. Specifically, x-rays are emitted through the body of the patient to determine the exact location of the contrast fluid. The resulting image may be transmitted to a monitor and a medical professional carrying out the procedure can then determine if the distal end of the needle is at the target site.
Existing biopsy needles are generally manufactured using a cannula made from stainless steel, nitinol, cobalt chromium, or other metal alloys. Using a needle made from such materials to take cytology or histology samples can have various negative effects. For example, oxides may form on the metal surface and the chemicals used in the cannula manufacturing process can remain on the inner surfaces of the needle. The contamination can be transferred from the needle lumen or stylet surface during sample collection and thus, the sample may become contaminated or the contamination may be passed into the patient.
Also, certain metal needles will take an induced shape set (bending) as the needle is advanced from the distal tip of the scope into the target tissue. The induced shape set makes subsequent needle passes to different areas of the anatomy difficult as the needle will not follow a straight line. The user may have to manually straighten the distal end of the needle after each needle pass or use more expensive metals to prevent shape set occurrence.
Additionally, if the needle is supplied with a metal stylet, high friction can occur between the stylet surface and the needle lumen. The metal-on-metal friction will lead to increased stylet removal forces when the device is in a difficult to reach anatomical location. Finally, injection of therapeutics through metal needles can cause contamination from the needle to be transferred into the patient with the therapeutic agents.
Polymer-body needles are known in the art (e.g., U.S. Pat. No. 5,092,848 to deCiutiis), but improved configurations are needed that provide desirable pushability, trackability, and columnar strength—particularly during use in gastrointestinal endoscopy procedures (including, for example, endoscopic retrograde cholangiography procedures).